Colossus faces off against PCs in code-breaking challenge

Valves vs transistors grudge match

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Colossus, the world’s first programmable digital computer, is back at work cracking codes at Bletchley Park for the first time in more than 60 years.

Colossus was developed by Britain in World War II to crack encrypted German messages. After years of painstaking restoration work a recreation of the machine returned to action today to mark the launch of the the fledgling National Museum of Computing.

Colossus has been put up against PCs in a code-breaking challenge. The match is more equal than it may seem at first sight- Colossus is a single-function device, and its speed at breaking codes rivals that of modern PCs.

Colossus is credited by some with shortening the war by months. It was capable of breaking messages within hours, revealing details of Germany's battle plans in the process.

The Mark I began operating in January 1944, and was succeeded in June the same year by the Mark II. Ten Mark II machines were built. Each machine featured 2,000 valves and was the size of a small lorry.

The rebuilt Colossus Mark II is being put to work deciphering a teleprinter message transmitted by radio from Paderborn in Germany, after it was first encrypted by one of the original Lorenz cipher machines used by the German High Command during World War II.

The Paderborn transmissions are being intercepted at Bletchley Park by two groups of amateur codebreakers, one using modern equipment and PCs and the other using World War II technology. Other amateur code breakers were also invited to join the challenge to intercept the transmission and to try to beat Colossus in cracking the 1938 Lorenz SZ42 encrypted message.

The challenge almost failed to get off the ground after the main transformer of the Lorenz machine developed a fault and the machine malfunctioned when it was tested on Wednesday. Fortunately, the team was able to repair the aging kit and return the cipher machine to service, fittingly in Bletchley Park’s Block H, the same buildings its predecessors were housed in during the war.

Andy Clark, a director and trustee at the National Museum of Computing, told El Reg that early attempts to intercept the transmissions using wartime radio equipment were hampered by "a lot of interference". So the Bletchley code-breakers were unable to get a decent copy until around 4.30pm. "We're getting unconfirmed reports that those with modern receivers, and using computers, have at least a partial result. We'll be starting Colossus off at 7.30am tomorrow morning," he said.

The code-breaking challenge marks the completion of the successful rebuild of Colossus and the start of a major fund-raising drive for the fledgling National Museum of Computing. It's the first time that Colossus has been used since then Prime Minister Winston Churchill ordered the destruction of the top-secret machine following the end of World War II.

The recreated Colossus is on public display at The National Museum of Computing at Bletchley Park, Buckinghamshire. This marks the fruits of a 14-year rebuilding project led by Tony Sale, a founder of the emerging Museum. The trustees of the Museum hope to raise £6m in investments to fully establish and run the facility. ®